Many vehicles, such as buses, are more stable if the suspension provides as wide a support base as possible. In addition, it is common practice to incorporate torque rods arranged in a parallelogram to provide stability and to eliminate the need for a torsion bar or roll bar. A suspension system directed to the forgoing that provides outrigger connections is described and illustrated in U.S. Pat. No. 4,596,402, the disclosure of which is incorporated by reference herein.
The present invention provides a suspension assembly that incorporates a new orintation of two torque rods relative to the axle and chassis of a vehicle. A longitudinal bolster beam is below the chassis. There are outrigger members on the chassis and the bolster beam so that, at the forward and rearward ends of the bolster beam, two air springs can be mounted outboard of the chassis. The axle is connected at the center of the bolster beam and there is a special axle bracket welded to the center of the bolster beam. Likewise, there is a special hanger bracket assembly supported from the chassis. The two torque rods are connected between the axle bracket and the hanger bracket. This suspension assembly is particularly adapted for installation on a vehicle having a rear-mounted engine. Thus, the engine rotates the wheels which push the axle, and the axle acts through the torque rods to pull the vehicle. According to the present invention, the two torque rods are mounted parallel to one another to define a parallelogram. However, the torque rods are offset from one another in three planes. The upper torque rod is outboard of the lower torque rod. The forward ends of the torque rods are outboard of their rearward ends. The upper torque rod is forward of the lower torque rod. The connections of the torque rods to the special bracket on the bolster beam are at points above and below the bolster beam. In addition, the forward end of the upper torque rod is forward and outboard of the forward end of the lower torque rod. The rearward ends of the torque rods are connected respectively to the hanger bracket assembly above and below the bolster beam. Also, the rearward end of the upper torque rod is forward and outboard of the rearward end of the lower torque rod. Nevertheless, the torque rods are of equal length and are identical to one another so that they are interchangeable, thereby reducing inventory requirements.
Because of the orintations of the torque rods, improved stability is provided in all directions. The axle is stabilized against torsional forces because of the vertically spaced connections of the parallelogram. Also, because of the angle of the torque rods as viewed in a horizontal plane, there is greater linear stability of the axle and lateral movement of the axle is effectively prevented.